Given the diversity of animal signals, there has been recent interest in categorizing signals into probable functions according to their properties. For example, models predict that signals of quality should be costly and condition dependent, whereas signals of individual identity should be cheap and expressed independently of condition. Here, we test these predictions by comparing the condition dependence of signals of individual identity and quality in Polistes wasps. Polistes fuscatus wasps have black and yellow patterns on the face and abdomen that signal individual identity, whereas Polistes dominulus wasps have black and yellow facial patterns that signal aspects of quality, related to dominance. We reared both species with and without supplemental food and examined the facial patterns of the resulting offspring. As predicted, food availability did not influence the development of identity signals in P. fuscatus. In strong contrast, P dominulus wasps reared with supplemental food had facial patterns that signaled higher levels of quality than P dominulus reared without supplemental food. Interestingly, the identity and quality signals have different condition dependence, despite being composed of similar pigments, suggesting that signal function has a stronger influence on signal properties than pigmentation. Because body size is often correlated with quality signal elaboration, we also tested how food supplementation influenced offspring size. In both species, supplemented colonies produced smaller offspring than nonsupplemented colonies, suggesting that queens may invest in producing fewer, larger offspring in stressful environments.
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